1. Field of the Invention
This invention relates to a drum brake actuating device and more particularly relates to a structure for connecting a brake cable as a remote force transmitting member to a brake lever which moves brake shoes to spread apart from each other.
2. Description of Related Art
A conventional drum brake actuating device, such as the one disclosed in the Japanese Utility Model Publication Number 61-18259, discloses a structure where a brake cable is actuated to pull a hooking/bending section on a free end of a brake lever at an inner side of the brake so as to cause a frictional engagement between brake shoes and a brake drum. The structure of the conventional device is disclosed in FIGS. 5 and 6. Terms, “upper”, “lower”, “right” and “left” in a description below refer to “upper”, “lower”, “right” and “left” in FIG. 5.
A pair of facing brake shoes 11, 12, each makes a T-shape in cross-section as a shoe rim 11a and a shoe web 11b combined together while a shoe rim 12a and a shoe web 12b combined together, and linings 11c, 12c are affixed on peripheral surfaces of the shoe rim 11a, 12a respectively. Each brake shoes 11, 12 is slidably pivotally supported on a back plate 10 fixed on a stationary portion of a vehicle by means of shoe-hold mechanisms 13, 14. Upper adjacent ends of the shoe webs 11b, 12b functionally engage with a wheel cylinder 15 fixed on the back plate 10, and lower adjacent ends of the shoe webs 11b, 12b are supported by an anchor block 16 fixed on the back plate 10. Further, the lower adjacent ends of the shoe webs 11b, 12b are restricted in the movement in a direction toward a bottom of the brake drum not shown in figures (i.e., in a direction away from the back plate 10) by means of a retaining plate 17 superposed on the anchor block 16 and fixed together.
A brake lever 18 superposed on and substantially parallel to a back surface of the shoe web 11b at the right side is designed such that a plate-like pivotal portion 18a thereof is pivotally supported on the upper end of the shoe web 11b by a pin 19. The brake lever 18 integrally forms a hooking/bending section 18c on a free end 18b thereof, and the section 18c is bending toward the back plate 10 at almost right angles at an inner side of the brake. The brake lever 18 integrally forms a projection 18d at an outer side of the brake, the projection 18d is abutting against an inner circumferential surface of the shoe rim 11a so as to restrict a returning position of the brake lever 18.
Further, as illustrated in FIG. 7, a through hole 18e enabling a later described cable end 27a to pass therethrough is formed on the free end 18b of the brake lever 18; and a narrow slit 18f being a slightly wider than a wire diameter of the inner cable 27 but narrower than an outside diameter of the cable end 27a directly extends therefrom.
Adjacent to the wheel cylinder 15, a shoe clearance adjustment mechanism 20 capable of adjusting the outer diameter of both brake shoes 11, 12 is extended between the shoe web 12b of the brake shoe 12 at the left side and the brake lever 18.
The shoe clearance adjustment mechanism 20 comprises an adjustment bolt 21, an adjustment nut 22 and a socket 23, where a left end of the adjustment bolt 21 nonrotatably abuts against the shoe web 12b at the left side and a right end of the socket 23 nonrotatably abuts against an intermediate portion of the brake lever 18 respectively.
An external thread 21a formed on a right side of the adjustment bolt 21 slidably fits into a cylindrical hole 23a of the socket 23, and a right end surface of the adjustment nut 22 screw-engaging with the external thread 21a abuts against an opening end surface of the cylindrical hole 23a. 
In the above-described shoe clearance adjustment mechanism 20, when adjustment teeth formed on a peripheral surface of the adjustment nut 22 is rotated using a tool inserted through a hole on the back plate 10 or the brake drum, the adjustment bolt 21 projects out from the socket 23 to adjust the shoe clearance as necessary.
Shoe return springs 24, 25 are extended between upper sides of the brake shoes 11, 12 and between lower sides of the brake shoes 11, 12 respectively and urge the brake shoes 11, 12 toward each other.
Although the drum brake of the above-described structure uses the wheel cylinder 15 as an actuating mechanism for the service brake and the brake lever 18 as an actuating mechanism for the parking brake, a drum brake may use the brake lever 18 as an actuating mechanism for both the service brake and parking brake, thereby eliminating the necessity of the wheel cylinder 15 in this application as for example employed in a golf cart.
The brake cable 26 comprises an inner cable 27 and an outer casing 28. A brake side of the inner cable 27 slidably positioned in the outer casing 28 is smoothly guided by a protrusion 10a formed on the back plate 10, thereby engaging a cable end 27a with the bending section.
A brake side of the outer casing 28 is designed such that a casing cap 28a fixed on an end thereof is installed on a pipe 30 fixed on the back plate 10. A coiled cable return spring 29 is contracted between the casing cap 28a and the bending section 18c of the brake lever 18. The other end of the inner cable 27 is connected to a parking brake operating device outside of figures and the other end of the outer casing 28 is fixed on a vehicle body. As is understood from an arrangement of the brake cable 26 above, the inner cable 27 within the brake is being sagged and flexibly deformed downward toward a bottom of the brake drum, not shown in FIG. 6, together with the cable return spring 29 as shown in two-dot chain line of FIG. 6 until the brake cable 26 at the parking brake operating device is fixed thereon.
Brake operation of the above-described structure is explained next.
The service brake operating device outside of figures is actuated to pressurize the wheel cylinder 15, and both brake shoes 11, 12 move to spread apart from each other around a pivot point with the anchor block 16, thereby causing frictional engagement between linings 11c, 12c and the rotating brake drum outside of figures.
As the parking brake operating device outside of figures is actuated to pull the inner cable 27, the brake lever 18 of FIG. 5 rotates clockwise around a pin 19 to move the left brake shoe 12 outward via the shoe clearance adjustment mechanism 20 and to move the right brake shoe 11 outward via the pin 19 around a point of abutment with the shoe clearance adjustment mechanism 20. Accordingly, both linings 11c, 12c frictionally engage with the brake drum to keep the drum's stationary condition.
The aforementioned drum brake of the related art has a drawback for example, when a back plate on which a long brake cable is being mounted or a brake assembly in which the brake cable is installed is conveyed onto a vehicle assembly line, or while the brake assembly is in land transport or maritime transport, it is possible to damage an inner cable and an outer casing and to give low efficient logistics because of its difficulty in boxing and packaging.